where is fx x2ex Concave down Solutionfx 2xex x2ex fx 2e
where is f(x)= (x^2)(e^x) Concave down ?
Solution
f\'(x) = 2xe^x + x^2e^x
f\'\'(x) = 2e^x + 2xe^x + 2xe^x + x^2e^x
= 2e^x + 4xe^x + x^2e^x
f\'\'(x) < 0
2e^x + 4xe^x + x^2e^x < 0
Therefore
e^x(x^2 + 4x + 2) < 0
As e^x can\'t be less than 0
So
(x^2 + 4x + 2) < 0
So
-2 - 2 < x < 2 - 2
So (-2 - 2 , 2 - 2)
